Tuning redox potentials of CO2 reduction catalysts for carbon photofixation by Si nanowires

Abstract

(Liu R)) plex polymer junction by Chardon-Noblat et al. [16]. The Faradic efficiency was measured at 63% in aqueous solutions. These results are encouraging because they show that catalysts can not only increase the efficiency when converting solar energy into chemical energy, but also increase the product selectivity by limiting the reaction pathway, especially for CO 2 photoreduction. Concurrently, our group has demonstrated that high product selectivity can be achieved by avoiding directly passing electrons to carbon in CO 2 [17,18]. Instead, when a reactive intermediate is activated by light-driven reactions, it binds with and reduces CO 2 in a highly specific manner. Our approach is inspired by dark reactions in natural photosynthesis. We have shown that the reactive intermediate can be a substrate or a metal catalyst (Scheme 1), the latter of which promises a broader scope of reactions. Building upon our previous success, herein we report that the redox potentials of the intermediate can be readily tuned to match the reducing power of the Si nanowire photocathode.Controlling redox potentials of catalysts is important because how they align with the energetics of the photoelectrode determines the ease or difficulty of charge transfer at the electrode/catalyst interface. For instance, for reduction reactions, the redox potential of the catalyst needs to be more negative than the Fermi level of the semiconductor to allow for the flow of electrons from semiconductor to catalyst. Additionally, the overpotential of the charge transfer from semiconductor to catalyst should be sufficiently small. All these considerations add extra challenges to find suitable semiconductor/catalyst pairs for practical CO 2 reduction. The semiconductors are limited by the following requirement in a high efficient photoelectrochemical cells: 1) suitable band gap to absorb large portion of solar light; 2) high-quantum efficiency of light to electron conversion; 3) long charge diffusion length of the bulk material to reduce charge recombination; 4) earth abundance for low cost at large scales. Only a handful of semiconductors meet these

Re(I) NHC Complexes for Electrocatalytic Conversion of CO2

“…As noted in the Introduction, ReCl­(bpy)­(CO) 3 is capable of mediating both photocatalytic and electrocatalytic CO 2 conversion, that is, the conversion of CO 2 at the potential of the first and second reduction, respectively. Given the promise of recent work in employing silicon substrates for photoelectrocatalysis, ,− we were interested in the ability of 1 and 2 to convert CO 2 at the first reduction potential. To that end, we examined the voltammetric response under argon and CO 2 saturation with added Brønsted acid (0.5 M PhOH).…”

Photo- and thermo-coupled electrocatalysis in carbon dioxide and methane conversion

“…In the past decade, a series of studies about heterogeneous photocatalysts, photo-catalytic systems and reactor design show a feasible route to convert CO 2 and CH 4 . However, the low yield is still a significant challenge in photocatalysis [2,3]. Accordingly, extensive reports propose that external bias input can significantly facilitate the electron-hole separation, and thus photocatalytic activity (Figs 2c and 3a) [4].…”

Photoelectrocatalytic activity of silicon nanowires decorated with electroless copper nanoparticles and graphene oxide using a plasma jet for removal of methyl orange under visible light

“…Silicon nanowires (Si NWs ) have gained interest in the last few years due to their versatility and properties like absorption, light emission, catalytic activity, and a wide range of applications. Among all its applications, they can be exploited for photocatalysis, [7][8][9][10] solar water splitting, 11,12 detection of molecules, [13][14][15] light trapping, 16,17 reduction of metals, 18 storage and energy conversion, 19 CO 2 reduction, 20,21 hydrogen generation, 22 and many other applications. Moreover, it has been reported that the decoration of silicon nanowires with metallic nanoparticles can enhance their catalytic properties, especially for electron discharging.…”